Common problems in Dacromet coating process

Today, in the process of the introduction of the most common problems, and we introduce briefly, so that you have more knowledge of the industry!
Dacromet coating process is the raw material into a water-soluble coating solution, and then directly coated on the surface of the activated workpiece, after drying, sintering to form a layer of inorganic film layer.
1, the coating fluid instability: Because the zinc powder density is relatively large, the disposition coating is extremely easy to precipitate, causes the coating liquid stratification, therefore must choose the highly effective thickening agent. The use of sodium polyacrylate to thicken the coating solution, when the addition of excess, the coating is very easy to gel, thus shortening the time limit. It is not suitable for the service life and production efficiency of the coating liquid.
2, coating the surface color: with advanced raw materials coated after the workpiece, the surface color after treatment is silvery white. In the process of production, it is found that the ratio of zinc powder and aluminum powder has a great effect on color, and increasing the amount of aluminum powder can increase the silver luster of the workpiece. After the increase of the amount of aluminum powder, the corrosion resistance of the workpiece has a certain effect;

3. The effect of ph value of chromic acid: There is a component, namely chromic acid solution, which must be considered in the application of the solution. In the actual preparation process, if the ph value of chromic acid is high, the chromic acid reacts very violently with the slurry, releasing a lot of heat, then making the whole solution system caking and invalidation. If again diluted with water after coating, the workpiece surface adhesion decreased, very easy to peel;
4, the effect of stirring time on the quality of zinc-chromium film: After the preparation of the coating liquid must be stirred, so that the slurry and chromic acid and other components are mixed evenly and the reaction curing, with a good coating liquid has a period of use, in a closed container storage, and stirring, can be used for 3 days;
5, the influence of wetting agent: the work of the workpiece are steel parts, coating liquid on the surface of the workpiece wetting, spreading good or bad, directly affect the quality of the layer. If the wetting, spreading is not good, will cause the workpiece surface leakage, need to apply several times to cover the surface of the workpiece, resulting in the coating unevenness to the coating.